1. Field of the Invention
The present invention relates generally to rotatable wedge valves that constitute improvements over the teachings of the Soderberg patents identified above. More specifically, the present invention concerns rotatable wedge valves having a rotatably actuated wedge member that has a geometry permitting force induced sealing with respect to seat members at both the open and closed positions of the rotatable wedge member. Even more specifically, the present invention is directed to a rotatable wedge valve mechanism that can be efficiently employed in replaceable cartridge valves as well as valves that must be assembled to or removed from a flow conduit as a valve unit.
2. Description of the Prior Art
Many valve types have been employed for stopping and controlling the flow of fluids in a pipe or other flow path. Each of these valves offers certain advantages while suffering from other disadvantages. These valve types include plug cock valves, ball valves, screw-down stop valves, angle valves, butterfly valves, gate valves and sluice valves.
A simple plug cock valve comprises a rotatable, tapered plug having a bore therethrough disposed in a complimentary tapered housing. The plug cock valve permits fluid flow to be fully stopped by rotating the plug not more than ninety degrees (90°). However, these valves offer only minimal graduated control of fluid flow by setting the plug cock at intermediate positions and require modification for use in high pressure environments.
Ball valves comprise a rotatable ball having a bore therethrough corresponding to the fluid flow path together with a seat for sealing with the ball surface. Ball valves operate similarly to the previously described plug cock valves and offer similar advantages and disadvantages. More accurate flow control is obtained with conventional screw-down stop valves wherein a circular sealing element is disposed on the end of a threaded actuator or stem for cooperation with a seat disposed about an opening through which the fluid flows. Rotation of the actuator gradually lifts the sealing element, such as a washer or other device, away from the seat to provide more accurate control of gradual changes in the fluid flow. A variation of the screw-down stop valve is the needle valve where the stem moves a tapered needle element linearly into a central opening of a circular seat member.
Conventional gate or sluice valves are often employed in high flow and high pressure operations. These valves comprise a solid gate which is moved perpendicularly into the fluid path to block the flow. These gates may have either flat or inclined sides forming a flat or wedge shaped gate which is moved generally perpendicular to the fluid flow by rotation of a threaded handle operatively connected thereto.
The valves described above fail to provide a valve operable between fully opened and fully closed positions in a quarter of one rotation or less while providing improved sealing in high pressure applications and shielding of the seat surface from erosion by the flowing fluid in both the opened and closed positions.
In the case of rotatable wedge valves it is well known that the rotatable wedge type valve element has a concave internal spherical surface portion that is engaged with the spherical external surface portion of a substantially immoveable core. The rotatable wedge element also defines an external convex spherical surface portion that is generated from a different center point as compared with the internal concave spherical surface and thus causes the valve element to have thick and thin wall portions. It is also known that the wall thickness of the rotatable wedge valve element increases gradually from its first leading end to its second or trailing end. Thus, in the closed position the thicker wall section of the rotatable wedge valve element will be positioned to apply a force to a valve seat, but in the open position of the rotatable wedge valve element the thin wall section will permit the valve element to have a range of movement within the valve chamber and permits the assembly and disassembly of the cartridge. It is desirable therefore to provide a rotatable wedge valve mechanism having a valve element geometry that causes development of seat engaging force at both the open and closed positions. It is also desirable to provide a method for manufacturing rotatable wedge valve members which permits the development of a variety of thick and thin wall sections that may be tailored to the needs of a customer.
It is well known that valves often become unserviceable and need repair or replacement. Especially in the case of rotatable wedge type valves it is typically necessary to shut down a flow line for an extended period of time during which the valve body is unbolted or otherwise released and removed from the flow line and replaced with another valve. It is desirable to provide a novel cartridge type rotatable wedge valve that can be efficiently restored for efficient service simply by removing and replacing a valve cartridge, thus eliminating the typical necessity to remove a valve housing from a flow line. Such cartridge valve is disclosed in U.S. Pat. App. Pub. No. US 2006/0196544 A1, the subject matter of which is incorporated herein by reference for all purposes.
Those skilled in the art have long sought and will appreciate the novel features of the present invention which solves these problems.